Probably just over anxious, but...

Normally she wakes after 40 minutes; to have had two naps this long is unheard of. When she's awake she's alert and happy, although starting to rub her eyes and get tired after about 2-2.5 hours. At night she's sleeping 7.30pm-6.45am-ish, with one wake for a feed somewhere between 3.30-5.30am.

This new sleeping pattern seems to have coincided with a gradual transferral to formula - I'm going back to work in September and trying to give up BF in a managed way. At the moment, she's having bottles at about 11am and 3pm, with BF at 7am, 7pm and when she wakes during the night. She takes about 6oz of formula each time, which is less than it says on the box, but she's pretty small for her age (9th centile) and seems happy to last out the four hours.

I'm probably being a bit PFB, but should I be concerned that she seems to be sleeping so much? I don't know if she's tiring herself out more now she can sit up and is making attempts at crawling, or whether maybe she's not getting enough nutrition from the feeds she's getting?

Can anyone reassure me that everythings ok? Will post this in behaviour and feeding threads in case anyone there has any ideas.